Method for manufacturing display device

ABSTRACT

A glass substrate of a display panel onto which an organic electroluminescence (EL) element or the like is formed is sealed by affixing the glass substrate and a sealing member such as a sealing glass onto which an adhesive has been applied. During this process, the temperature of the adhesive is controlled by, for example, controlling the temperature of the nitrogen gas to fill a chamber through a temperature adjusting device, so that the viscosity of the adhesive is adjusted. In this manner, quick and precise sealing of the display substrate by the sealing member and the adhesive can be achieved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method for manufacturing adisplay device for displaying text, images, etc.

[0003] 2. Description of the Related Art

[0004] In general, display panels used in electroluminescence (EL)display devices and in liquid crystal display devices are constructed toinclude display substrates onto which display elements such as, forexample, a light emitting element, liquid crystal, and a driving elementfor driving the light emitting element or liquid crystal are provided.Normally, in order to maintain the function and quality of the displaysubstrate, the display substrate is sealed with a suitable sealingmember. Examples of materials used for such a sealing member includemetal and glass. The display substrate is affixed to the sealing memberby an adhesive and sealed. The quality of sealing of the displaysubstrate in the display panel is an important factor for determiningthe quality and lifetime of the display device.

[0005]FIG. 1 schematically shows how a display substrate is sealed by asealing member.

[0006] As shown in FIGS. 1(a) and 1(b), element layers 32 which willbecome the display regions are formed through a thin film formationprocess on one side of a glass substrate 31 which is a type of displaysubstrate 33. FIGS. 1(a) and 1(b) show an example configuration in whicha plurality of (twelve) element layers 32 and a plurality of (twelve)display substrates 33 are simultaneously formed on a glass substrate 31for simultaneously manufacturing a plurality of (twelve) display panels.The position of the glass substrate 31 relative to a sealing glass 34which is the sealing member placed to oppose the element layers 32 isdetermined by an image processor or the like which recognizes one ormore positioning marks 39 on the sealing glass 34. Then, the glasssubstrate 31 is moved in the Z direction shown in FIG. 1(a) and isaffixed to the sealing glass 34. On the sealing glass 34, an adhesive 35is applied in advance in a manner to surround the display regions alongthe shape to be sealed of the display substrates 33 (more specifically,their element layers 32). The surface of the sealing glass 34 opposingthe display substrate 33 is engraved through etching or the like tocorrespond to the shapes and arrangement of the element layers 32. Theengraved section 36 of the sealing glass 34 is provided for applying anabsorbent or the like for maintaining the characteristics of the displaysubstrate 33 to be sealed. In FIG. 1(b), the glass substrate 31 is notshown.

[0007]FIG. 2 schematically shows the cross section of the structure whenthe glass substrate 31 and the sealing glass 34 are affixed. The glasssubstrate 31 is held to a supporting member 37 using vacuum suction andaffixed to the sealing glass 34 which is placed on a base (not shown).During this process, as shown in FIG. 2, the glass substrate 31 and thesealing glass 34 are pressed so that a predetermined gap G is formedbetween the glass substrate 31 and the sealing glass 34. After the gap Gis adjusted to the predetermined value, a curing process for theadhesive 35 is applied and the display substrate 33 is sealed by thesealing glass 34. During this sealing process, the width of the portionof the glass substrate 31 and of the sealing glass 34 in contact withthe adhesive 35, that is, the seal line width W, is determined by theamount and viscosity of the adhesive 35, the gap G, the magnitude andduration of the applied pressure, etc. Also, a spacer 38 having acylindrical or a spherical shape with a predetermined diameter, forexample, is provided within the adhesive 35 (schematically shown in FIG.2) so that a predetermined gap G can be obtained using the spacer 38 asa stopper for the pressure application.

[0008] Normally, a resinous adhesive is used as the adhesive 35. When aresinous adhesive is used, the material of the resin is selected basedon the type of display substrate 33, the object of sealing, etc.However, for some of these resins, the viscosity cannot be adjusted.

[0009] For example, for a display substrate used in a display panel ofan EL display device, that is, a display substrate 33 onto which an ELelement is formed at the element layer 32, because an EL element hascharacteristics that its heat endurance is low and an EL element iseasily degraded by moisture, an ultraviolet curable epoxy resin whichhas low permeability for water and, in addition, which does not requireheating for curing is used as the adhesive 35. Because the ultravioletcurable epoxy resin is not diluted by any solvent, in general, theultraviolet curable epoxy resin has a high viscosity and cannot beadjusted to a viscosity at which the resin can be easily used. Inaddition, if the viscosity is adjusted by changing the constitution ofthe ultraviolet curable epoxy resin, it is difficult to maintain the lowwater permeability characteristic of the resin.

[0010] When a resin having a high viscosity as described above is usedas the adhesive 35, it is necessary, during the affixing of the glasssubstrate 31 and the sealing glass 34 as described above, to apply ahigher pressure on the affixing surfaces of the substrate 31 and thesealing glass 34 to allow the gap G to reach a desired value and, at thesame time, secure the seal line width W. However, if the magnitude ofthe applied pressure is rapidly increased, the adhesive 35 having a highviscosity cannot change its shape to respond to the change in thepressure, and affixing defects such as shown by dotted lines in FIG. 3which is a plan view of the sealing glass 34 may be generated.

[0011] More specifically, when the adhesive 35 does not follow thechange in the applied pressure and the gap G does not uniformly reach adesired value, defects such as (A) creation of a seal path through whichthe gas remaining in the inner space to be sealed can escape, (B)instability of the seal line width W, and (C) deviation of the adhesive35 from the predetermined sealing position, may be generated. These aremarked with the respective labels A, B, and C in FIG. 3. These affixingdefects not only cause shape defects, but may also adversely affect thequality and lifetime of the EL display device by, for example, creatinga sealing defect, causing the pressurized gas to remain inside, orincreasing water permeability.

[0012] In addition to affecting the above described display substrateonto which an EL element is formed, the above-described disadvantagesare common when sealing any display panel, such as, for example, aliquid crystal display substrate and a plasma display substrate, whenthe display substrate is sealed using a suitable sealing member and ahighly viscous resin adhesive.

SUMMARY OF THE INVENTION

[0013] The present invention was conceived to solve the above describedproblems and one object of the present invention is to quickly andprecisely seal an element substrate with a sealing member and anadhesive.

[0014] In order to achieve at least this object, according to one aspectof the present invention, there is provided a method for manufacturing adisplay device in which an element substrate and a sealing substrate areaffixed via an adhesive therebetween, wherein a display element isformed on the element substrate, the sealing substrate is placed tooppose the element substrate at the side onto which the display elementis formed, and the adhesive is provided at positions to surround theformation region of the element; the element substrate and the sealingsubstrate affixed to each other are pressed; and the adhesive is cured;and wherein an ultraviolet curable resin is used as the adhesive; andthe temperature of the adhesive is controlled before the adhesive iscured by irradiation of ultraviolet light.

[0015] According to another aspect of the present invention, it ispreferable that, in the method for manufacturing, the adhesive is heatedto a predetermined temperature before the element substrate and thesealing substrate affixed to each other via the adhesive there betweenare pressed. Or, alternatively, according to another aspect of thepresent invention, it is preferable that, in the method formanufacturing, the adhesive is heated to a predetermined temperaturewhile the element substrate and the sealing substrate affixed to eachother via the adhesive therebetween are pressed.

[0016] When, for example, a cation polymerizing, ultraviolet curableepoxy resin is used as the adhesive, by appropriately controlling thetemperature of the adhesive, it is possible to appropriately control theviscosity of the resin or the like. In other words, even when anadhesive having a high viscosity at room temperature is employed, it ispossible to control the viscosity by controlling the temperature. Forexample, by heating the adhesive to a predetermined temperature, theviscosity of the adhesive can be adjusted such that a desirabledeformation rate of the adhesive can be realized when the substrates areaffixed and pressed. Therefore, it is possible to quickly and preciselyperform the operations for pressing the substrates, rolling the adhesiveto a designated sealing width, and curing the adhesive.

[0017] In addition, by employing an ultraviolet curable epoxy resin asthe adhesive, the resin can be cured by irradiation of ultravioletlight. Therefore, even when, for example, an organic electroluminescenceelement is employed as the display element, it is possible to prevent,during curing of the resin, exposure of the display element to a hightemperature environment which may degrade the element characteristics,and thus a highly reliable display device can be obtained.

[0018] According to another aspect of the present invention, it ispreferable that, in the method for manufacturing, the temperature of theadhesive is controlled based on application conditions of the pressurefor pressing the element substrate and the sealing substrate.

[0019] When the affixed substrates are pressed, the adhesive providedbetween the substrates deforms at a rate based on the applied pressureand the viscosity of the adhesive at that point. Therefore, when theviscosity of the adhesive is adjusted by controlling the temperature ofthe adhesive, it is possible to realize quick and reliable adhering ofthe substrates by the adhesive in consideration of the applied pressure.

[0020] According to another aspect of the present invention, it ispreferable that, in the method for manufacturing, the pressure forpressing the element substrate and the sealing substrate is changed overtime until a target gap is achieved between the element substrate andthe sealing substrate affixed to each other. According to another aspectof the present invention, it is preferable that, in the method formanufacturing, the pressure for pressing the element substrate and thesealing substrate is changed over time by repeating a pressure changingperiod in which the pressure is changed and a pressure retaining periodin which a constant pressure is maintained. According to another aspectof the present invention, it is preferable that, in the method formanufacturing, a plurality of the pressure changing periods and aplurality of the pressure retaining periods are repeated, and theduration of each of the plurality of pressure retaining periods isindependently set to an arbitrary length. According to another aspect ofthe present invention, it is preferable that, in the method formanufacturing, a plurality of the pressure changing periods and aplurality of the pressure retaining periods are repeated, and the amountof change in pressure for each of the plurality of pressure changingperiods is independently set to an arbitrary value.

[0021] According to another aspect of the present invention, it ispreferable that, in the method for manufacturing, the pressure ischanged over time through 3 repetition of pressure changing periods inwhich pressure is changed and pressure retaining periods in which aconstant pressure is maintained.

[0022] In this manner, by changing the pressure for pressing thesubstrates over time based on various conditions, in addition tocontrolling the temperature of the adhesive, it is easy to obtain auniform seal width and a uniform gap. In addition, by varying theapplied pressure, it is possible to reliably deform the adhesive betweenthe element substrate and sealing substrate by pressing, to easilycontrol the deformation of the adhesive to be uniform at each position,and to obtain a uniform gap between the substrates and a uniform contactarea (seal width) of the adhesive with respect to the affixing surfacesof the sealing substrate and the element substrate.

[0023] Moreover, as described above, by controlling the change over timeof the applied pressure in stages, increasing the applied pressure instages, or changing the applied pressure over time while monitoring thegap, precise and quick sealing process is facilitated.

[0024] Furthermore, the applied pressure can be changed, the pressurechanging periods and pressure retaining periods can be repeated, and theconditions of each period can be set with a large degree of freedom inconsideration of the characteristics of the adhesive or the like,allowing for smooth and uniform deformation of the adhesive providedbetween the substrates in response to the pressure for pressing thesubstrates. Therefore, quick sealing of the element substrate with thesealing substrate can be achieved while maintaining a superior quality.

[0025] Also, because a precise and quick sealing can be achieved througha simple controlling method of repeating pressure changing periods andpressure retaining periods under suitable conditions, the method issignificantly advantageous also in reducing the manufacturing cost.

[0026] According to another aspect of the present invention, it ispreferable that, in the method for manufacturing, the amount of changein pressure for a final pressure changing period among the plurality ofpressure changing periods is smaller than the amount of change inpressure for any of the previous pressure changing periods.

[0027] According to another aspect of the present invention, it ispreferable that, in the method for manufacturing, the rate of change ofpressure in at least one of the plurality of pressure changing periodsdiffers from rates of change of pressure in the other periods.

[0028] For an adhesive having a relatively high viscosity, even when thetemperature, for example, is controlled, the deformation rate inresponse to the pressure application is still reduced as the appliedpressure is increased. Therefore, by setting the pressure changes sothat the amount of change in pressure is smaller for a later periodamong a plurality of pressure changing periods, it is possible touniformly deform such an adhesive while allowing reliable response tothe applied pressure. Moreover, the deformation rate of the adhesive,that is, the inter-substrate gap can be controlled at a high precisionwith respect to the target inter-substrate gap, and thus, the sealingquality can be improved.

[0029] In addition, by making the pressure changing rate variable foreach period, it is possible to uniformly and quickly deform the adhesiveby pressing the substrates under optimal conditions based on thecharacteristics of the adhesive to be employed and to improve thesealing quality.

DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is an explanatory diagram showing sealing, with a sealingglass, of a plurality of display substrates formed on a glass substrateaccording to a method for manufacturing a display panel of a relatedart.

[0031]FIG. 2 is an enlarged schematic cross sectional view of the glasssubstrate and the sealing glass affixed according to the related art.

[0032]FIG. 3 is a plan view showing example sealing defects in a methodfor manufacturing a display panel in the related art.

[0033]FIG. 4 is an explanatory diagram showing an example devicestructure for practicing a first embodiment of a method formanufacturing a display panel according to the present invention.

[0034]FIG. 5 is a graph showing a relationship between the temperatureand viscosity of a cation polymerizing, ultraviolet curable epoxy resinwhich is used as an adhesive in the first embodiment of the presentinvention.

[0035]FIG. 6 is a plan view showing an example structure of an elementlayer of an organic EL display panel.

[0036]FIGS. 7A and 7B are cross sectional diagrams showing an examplestructure of an element layer of an organic EL display panel.

[0037]FIG. 8 is an explanatory diagram showing an example devicestructure for practicing a second embodiment of a method formanufacturing a display panel according to the present invention.

[0038]FIG. 9 is a time chart showing an example pattern for applicationof pressure for pressing the affixing surfaces between the displaysubstrate and the sealing glass in the second embodiment according tothe present invention.

[0039]FIG. 10 is a schematic cross sectional view for explainingdeformation of the adhesive.

[0040]FIG. 11 is an explanatory diagram showing an example devicestructure for practicing an alternate configuration of a first or secondembodiment according to the present invention.

[0041]FIG. 12 is an explanatory diagram showing an example devicestructure for practicing a further alternate configuration of a first ora second embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0042] (First Embodiment)

[0043] A first preferred embodiment of a method for manufacturing adisplay panel of a display device according to the present inventionwill now be described referring to FIGS. 4 and 5 using an example inwhich the method is used for manufacturing a display panel having adisplay substrate (element substrate) constructed to include an organicEL element as the display element. In the first embodiment, similar tothe conventional art exemplified above and shown in FIGS. 1 and 2, forsealing, with a sealing member (in the embodiments, glass; hereinafterreferred to as “sealing glass”), the display substrate constructed byforming an element layer on a glass substrate, an adhesive is applied inadvance on the affixing surface between the sealing glass and thedisplay substrate in a manner to surround the display regions of thedisplay substrate. After the sealing glass and the display substrate areaffixed, a pressure is applied to the affixing surface. Then, after thegap between the sealing glass and the display substrate has reached atarget value, the adhesive is cured. The pressure to be applied may beconstant, or, alternatively, may be changed over time as will bedescribed below relative to other embodiments of the present invention.

[0044]FIG. 4 is a schematic diagram showing an example structure of anapparatus for manufacturing a display panel by the method formanufacturing according to the first embodiment.

[0045] As shown in FIG. 4, on one surface of glass substrates 1 whichare a type of a display substrate 3, element layers 2 constructed froman organic EL element or the like are formed through a thin filmformation process. Again, in this structure, similar to FIG. 1, forexample, a plurality of element layers 2 are simultaneously formed on aglass substrate 1 (mother substrate) and a plurality of displaysubstrates 3 are simultaneously created so that a plurality of displaypanels are manufactured simultaneously. The glass substrate 1 is affixed(adhered) to a sealing glass 4, which is a sealing member placed tooppose the element layers 2. On the sealing glass 4, an adhesive 5 isapplied in a manner to surround the display substrate 3, that is, alongthe shape for sealing the element layers 2. The adhesive 5 is made of anultraviolet curable resin having a high viscosity, for example, a cationpolymerizing, to ultraviolet curable epoxy resin. The cationpolymerizing, ultraviolet curable epoxy resin is well suited for anapplication to seal the organic EL element or the like because the resinhas characteristics of low contraction ratio during curing process andlow permeability for water. In addition, the surface of the sealingglass 4 which opposes the display substrate 3 is engraved throughetching or the like to correspond to the shape and arrangement of thedisplay substrates 3 (more specifically, their element layers 2). Theengraved section 6 of the sealing glass 4 is provided for applying anabsorbent or the like for maintaining the characteristics of the displaysubstrate 3 to be sealed.

[0046] Each of the above described members is placed in a chamber 20.The inside of the chamber 20 is filled with nitrogen gas (N₂) which issupplied to and discharged from the chamber 20 through a respective gasintroduction port 21 a and gas discharging port 21 b. In order toprevent degradation of the organic EL element by the moisture present inthe atmosphere, nitrogen gas having a moisture content of 5 ppm or lessis used. Also, the temperature of nitrogen gas to fill the chamber 20can be controlled by a temperature adjusting device 26 provided at thegas introduction port 21 a. By controlling the temperature of nitrogengas, it is possible to simultaneously control the temperature of theadhesive 5.

[0047] In the chamber 20, the glass substrate 1 is vacuum suctioned to asupporting member 7 provided within the chamber 20. The position of thesupporting member 7 is controlled. In FIG. 4, the apparatus (mechanism)for vacuum suctioning the glass substrate 1 is not shown. On the otherhand, the sealing glass 4 is placed on a quartz glass 11 which isinstalled at the bottom surface of the chamber 20. An apparatus 24 forcontrolling the position of the supporting member 7 moves the supportingmember 7 and the glass substrate 1 in the horizontal direction based onan image of, for example, one or more positioning marks (not shown)which are imaged by one or more CCD cameras 22 provided within thechamber 20, and determines the relative position of the supportingmember 7 and the glass substrate 1 with respect to the sealing glass 4.After the positioning process is completed, an apparatus for applying apressure to the supporting member 7 (not shown) applies a pressure tothe supporting member 7 and the glass substrate 1 in the direction shownby the arrow towards the sealing glass 4 so that pressure is applied atthe affixing surfaces of the glass substrate 1 and the sealing glass 4.In the manufacturing apparatus shown in FIG. 4, the reference numeral 23denotes an ultraviolet light source for irradiating ultravioletradiation through the quartz glass 11 and the sealing glass 4 onto theadhesive 5 composed of the cation polymerizing, ultraviolet curableepoxy resin, for curing the adhesive 5.

[0048] Next, a method for manufacturing a display panel of an EL displaydevice according to the first embodiment using such an apparatus will bedescribed.

[0049] In the first embodiment, the sealing process is performed whilecontrolling the temperature of the nitrogen gas. If the set temperatureis too high, the characteristics of the organic EL element formed on thedisplay substrate 3 are degraded and, moreover, the viscosity of theadhesive 5 may become too low such that the adhesive may flow away fromthe affixing surface. Because of this, in order to seal the displaysubstrate 3 in a desired manner, it is preferable to set the temperaturewithin the chamber 20, that is, the temperature of the nitrogen gas, ina suitable temperature range, taking into consideration the relationshipwith respect to the pressure to be applied.

[0050]FIG. 5 is a graph showing the relationship between the temperatureand the viscosity of the adhesive 5 formed of a cation polymerizing,ultraviolet curable epoxy resin used in the first embodiment. It hasbeen found that the viscosity of this adhesive 5 rapidly decreases asthe temperature rises, as shown in FIG. 5. Normally, the standardtemperature of the clean room in which the sealing process is performedis approximately 24° C. The temperature of the adhesive 5 is equal tothis temperature of 24° C., and as shown in FIG. 5, the viscosity of theadhesive at this temperature is high and exceeds 100000 mPa·sec. Thisproperty of the adhesive constitutes a barrier to quick and accuratesealing of the display substrate.

[0051] In the first embodiment, the temperature of nitrogen gas fillingthe chamber 20 is set at 35° C. prior to the irradiation of the adhesive5 with ultraviolet light. With this process, the temperature of theadhesive 5 is also set approximately at 35° C. As shown in FIG. 5, theviscosity of the adhesive 5 at this temperature of 35° C. isapproximately 34000 mPa·sec which is one order of magnitude smaller thanthe viscosity at the standard temperature of the clean room,approximately 24° C. More importantly, at the temperature of 35° C., thecharacteristics of the organic EL element formed on the displaysubstrate is not degraded by the heat.

[0052] In this manner, while the temperature of the adhesive 5 ismaintained at approximately 35° C., the position controller 24 isoperated based on one or more images obtained by one or more CCD cameras22 to determine the horizontal position of the glass substrate 1relative to the sealing glass 4. After the positioning process, thesupporting member 7 which supports the glass substrate 1 is verticallylowered towards the sealing glass 4 and a pressure is applied to theaffixing surface between the display substrate 3 and the sealing glass4. Through this pressure, the adhesive 5 controlled to be at the settemperature as described above is desirably deformed and the gap Gbetween the affixing surfaces can easily reach its target value. Afterthe gap G has reached the target value, the ultraviolet light source 23is switched on in order to irradiate ultraviolet light onto the adhesive5 to cure the adhesive 5 and thereby seal the display substrate 3 withthe sealing glass 4.

[0053] For reference, an example structure of an element layer 2 formedon the display substrate 3 which is used as the organic EL display panelwill now be described.

[0054]FIG. 6 is an enlarged plan view of a pixel and its periphery of anactive matrix type EL display panel in which a thin film transistor(TFT) which is an active element is added for each EL element forming adisplay unit (pixel) of the display device.

[0055] The EL display panel is a display device which takes advantage ofthe property of an EL element which emits light when an electric fieldis applied. On a display substrate, gate signal lines for drivingswitching TFTs and signal lines for allowing display of each pixel areformed in rows and columns in a matrix form.

[0056] As shown in FIG. 6, in the EL display panel, gate signal lines 51and drain signal lines 52 are formed as the signal lines as describedabove. Organic EL elements 60 are formed as pixels corresponding to theintersections of these signal lines. In the EL display panel, in orderto realize a full-color display, repeating units are formed eachconsisting of three types of organic EL element 60R, 60G, and 60B havingdifferent emission colors. These three types of EL elements form a groupto constitute a display unit as a full-color display device for emittinglight of a desired color.

[0057] In the vicinity of an intersection between the signal lines, aTFT 70 which is switched by the gate signal line 51 is formed. When theTFT 70 is switched “ON”, the signal on the drain signal line (datasignal line) 52 is connected to the source 73S and applied to acapacitor electrode 55. The capacitor electrode 55 is connected to agate 81 of a TFT 80 for driving an EL element. The source 83S of the TFT80 is connected to an anode 61 of the organic EL element 60 and thedrain 83D of the TFT 80 is connected to the driving power supply line 53which functions as an electric current source for supplying electriccurrent to the organic EL element 60.

[0058] Corresponding to the TFTs 70 and 80, a storage capacitorelectrode line 51 is formed parallel to the gate signal line 51. Thestorage capacitor electrode line 54 is formed of, for example, a metalsuch as chromium (Cr), similar to the gate signal line 51. The storagecapacitor electrode line 54 and the capacitor electrode 55 which isplaced to oppose the storage capacitor electrode line 54 with aninsulative film in between constitute a capacitor element (storagecapacitor) in which charges are accumulated. The storage capacitor isprovided for maintaining the voltage applied to the gate electrode 81 ofthe TFT 80.

[0059]FIGS. 7A and 7B show cross sections near the pixel shown in FIG.6. FIG. 7A shows a cross section along the line D-D in FIG. 6 and FIG.7B shows a cross section along the line E-E in FIG. 6. As shown in FIGS.7A and 7B, the element layer of the display substrate in the organic ELdisplay panel is formed by sequentially layering the TFT and the organicEL element 60 on substrate 90 such as a glass substrate, a synthesizedresin substrate, a conductor substrate, or a semiconductor substrate.

[0060] The formation process of the TFT 70 for controlling thecharging/discharging of the capacitor electrode 55 will first bedescribed.

[0061] As shown in FIG. 7A, on an insulative substrate 90 made of quartzglass, non-alkali glass, or the like, an active layer 73 is formed whichis made of a polycrystalline silicon film obtained by polycrystallizingan amorphous silicon film through irradiation of laser. In the activelayer 73, a structure commonly known as an LDD (Lightly Doped Drain)structure is created. More specifically, on both sides of the channel,low concentration regions 73LD are provided, and further a source 73Sand a drain 73D which are high concentration regions are providedoutside the LD region 73LD. Over the active layer 73, a gate insulativefilm 92 and a gate electrode 71 which constitute a portion of the gatesignal line 51 made of a high melting point metal such as Cr andmolybdenum (Mo) are formed. At the same time, the storage capacitorelectrode 54 is also formed. Then, an interlayer insulative film 95having a structure in which a silicon oxide film (SiO₂ film) and asilicon nitride film (SiN film) are layered in that order is formed overthe entire surface of the gate insulative film 92. A contact hole isformed to correspond to the drain 73D and is filled with a metal such asaluminum (Al). The drain signal line 52 and a drain electrode 96 whichforms a part of the drain signal line 52 are then formed. Over the filmsurface, a planarization insulative film 97 is provided for planarizingthe surface, the film 97 being made of, for example, an organic resin.

[0062] Next, the formation process of the TFT 80 for driving the organicEL element 60 to emit light will be described. In FIG. 7B, structuresformed of the same material as, and simultaneously with, the structuresdescribed above with reference to FIG. 7A are generally assigned thesame reference numerals.

[0063] As shown in FIG. 7B, on the insulative substrate 90 as describedabove and made of quartz glass, non-alkali glass, or the like, an activelayer 83 made of the polycrystalline silicon film is formedsimultaneously with the active layer 73 of the TFT 70. In the activelayer 83, a channel 83C which is intrinsic or substantially intrinsic isprovided below the gate electrode 81 and a source 83S and a drain 83Dare provided at both sides of the channel 83C by ion doping a p-typeimpurity, so that a p-type channel TFT is formed. Over the active layer83, the gate insulative film 92 and the gate electrode 81 made of a highmelting point metal such as Cr and Mo are formed.

[0064] The gate electrode 81 is formed simultaneously with the gateelectrode 71 in FIG. 7A, and is connected to the source 73S of the TFT70 as described above. Over the entire surface of the gate insulativefilm 92 and the gate electrode 81, an interlayer insulative film 95 isformed in which a SiO₂ film and a SiN film are layered in that order. Acontact hole is formed to correspond to the drain 83D and is filled witha metal such as Al. At the same time, the driving power supply line 53is formed. Furthermore, over the film surface, a planarizationinsulative film 97 is formed for planarizing the surface, the film 97being made of, for example, an organic resin. A contact hole is formedin the planarization insulative film 97 to allow a connection to thesource 83S and a transparent electrode 61 which is to be connected tothe source 83S through the contact hole is formed on the planarizationinsulative film 97. The transparent electrode 61 constitutes the anodeof the organic EL element, and allows transmission, towards the side ofthe substrate 90, of light emitted from the organic EL element 60 to belayered on top of the transparent electrode 61. As the transparentelectrode 61, for example, an ITO (Indium Tin Oxide) which is an oxideof indium and tin is used.

[0065] The organic EL element 60 is constructed by forming and layeringa light emitting element layer 66 and an Al cathode 67 in that order ontop of the anode 61. The light emitting element layer 66 further has afour-layer structure, each structure formed and layered above the anode61 in order and made of a material, for example, as described below.

[0066] (1) Hole transport layer 62: “NPB”

[0067] (2) Emissive layer 63: following materials are used correspondingto each of different emission colors

[0068] Red—A host material “Alq₃” doped with “DCJTB”

[0069] Green—A host material “Alq₃” doped with “coumarin 6”

[0070] Blue—A host material “BAlq” doped with “perylene”

[0071] (3) Electron transport layer 64: “Alq₃”

[0072] (4) Electron injection layer 65: lithium fluoride (LiF)

[0073] The abbreviations used above for describing the materialsrepresent the following compounds.

[0074] “NPB”—N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine

[0075] “Alq₃”—Tris(8-hydroxyquinolinato)aluminum

[0076]“DCJTB”(2-(1,1-dimethylethyl)-6-(2-(2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl)-4H-pyran-4-ylidene)propanedinitrile

[0077] “Coumarin 6”—3-(2-benzothiazolyl)-7-(diethylamino)coumarin

[0078]“BAlq”—(1,1′-bisphenyl-4-olato)bis(2-methyl-8-quinolinplate-N1,08)aluminum

[0079] The hole transport layer 62, electron transport layer 64,electron injection layer 65, and cathode 67 are formed to be common foreach of the organic EL elements 60 corresponding to a pixel as shown inFIG. 6. An island-like emissive layer 63 is formed corresponding to theanode 61. At the periphery of the anode 61, an insulative film(planarization insulative film) 68 made of an organic resin or the likeis formed (outside the region shown by dotted lines in FIG. 6). Thisfilm is provided in order to prevent shortage of the cathode 67 andanode 60 caused by cracking of the emissive layer 63 due to the stepcreated by the thickness of anode to 61.

[0080] When the pixel of the organic EL element 60 formed as describedabove is driven by the TFTs 70 and 80, holes injected from the anode 61and the electrons injected from the cathode 67 are recombined within theemissive layer 63 and light is emitted.

[0081] When the above materials are used for each of the layersconstituting the organic EL element 60, it is preferable to set thetemperature that can be applied to the element layer 2 to 95° C. orless, in order to prevent degradation of characteristics of each layer.

[0082] By forming layers up to the cathode 67 on the substrate 90 asdescribed above, a display substrate 3 as shown in FIG. 4 can beobtained. A sealing glass 4 and the obtained display substrate 3 areaffixed through the above described method.

[0083] By affixing in this manner, in a method for manufacturing adisplay panel according to the first embodiment, the followingadvantages can be obtained.

[0084] (1) When the glass substrate 1 is sealed with the sealing glass4, in consideration of the relationship between the viscosity of theadhesive 5 and the pressure applied to the affixing surface of the glasssubstrate 1 and the sealing glass 4, the temperature of the adhesive 5is controlled so that the viscosity of the adhesive is at an appropriatevalue. Because of this, the shape of the adhesive 5 can be deformedquickly and smoothly in response to the pressure applied to the affixingsurface.

[0085] (2) In this manner, the length of time required for achieving atarget gap G of the affixing surfaces can be shortened.

[0086] (3) Moreover, because a more uniform gap G can be obtained at theaffixing surface, the seal line width W is also stabilized, and, thus, ahigh quality seal can be provided for the display substrate 3.

[0087] (4) By controlling the temperature of nitrogen gas filling thechamber 20 to 35° C., it is possible to prevent degradation in thecharacteristics of the organic EL element formed on the displaysubstrate 3.

[0088] (5) Moreover, by performing the sealing process in a nitrogen gasatmosphere having low moisture content, it is possible to minimize themoisture content remaining within the sealed space.

[0089] (Second Embodiment)

[0090] A method for manufacturing a display panel according to a secondembodiment of the present invention will now be described referring toFIGS. 8 and 9. Similar as in the first embodiment, the second embodimentwill be described using an example case in which the method is appliedas a method for manufacturing a display panel having a display substrateconstructed to include an organic EL element. In the following, thedescription focuses primarily on the structures differing from those ofthe first embodiment.

[0091] In the second embodiment, the device for applying a pressure tothe supporting member 7 during the sealing process in the firstembodiment further includes a function to monitor the applied pressure.This device for applying a pressure is shown in FIG. 8 as a pressurecontroller 25 which can arbitrarily control the applied pressure whilemonitoring the applied pressure.

[0092] In the second embodiment, the pressure applied to the affixingsurfaces between the glass substrate 1 and the sealing glass 4 by thepressure controller 25 is changed over time to effect sealing.

[0093]FIG. 9 is a time chart showing an example pattern of pressureapplication by the pressure controller 25 for the supporting member 7.In the second embodiment, the temperature of nitrogen gas filling thechamber 20 is set at 35° C. which is identical to the set value of thetemperature in the first embodiment.

[0094] In this second embodiment, the relative position between theglass substrate 1 and the sealing glass 4 is determined using theposition controller 24 for the supporting member 7, and then a pressureis applied to the affixing surface between the glass substrate 1 and thesealing glass 4 according to the pressure application pattern shown inFIG. 9.

[0095] In this pressure application pattern, pressure is appliedaccording to the following three conditions, (i), (ii), and (iii).

[0096] (i) Pressure changing periods (periods T₁, T₃, and T₅ in FIG. 9)in which the pressure is changed (increased) at a constant rate andpressure retaining periods (periods T₂, T₄, and T₆ in FIG. 9) in whichthe changed (increased) pressure is retained at a constant pressure arerepeated so that the pressure and gap reach their respective targetvalues.

[0097] (ii) The lengths of the pressure retaining periods T₂, T₄, and T₆are set to equal to each other as indicated by the following equation.

T₂=T₄=T₆

[0098] (iii) The amount of change (amount of increase) δP5 of thepressure at the final pressure changing period T₅ is set to be smallerthan the respective amounts of change (amounts of increase) δP1 and δP3of pressure at the previous pressure changing periods, T₁ and T₃. Inother words, the amounts of change δP1, δP3, and δP5 satisfy thefollowing relationships. In the example process shown in FIG. 9, δP1 andδP3 are equal to 0.2 kgw/cm² and δP5 is equal to 0.1 kgw/cm².

δP1>δP5

δP3>δP5

[0099] In this manner, by applying a pressure of a predetermined patternto the affixing surface between the glass substrate 1 and the sealingglass 4, the gap G reaches its target value at least at the pressureretaining period T₆, with the spacer (denoted by reference numeral 38 inFIG. 2) provided within the adhesive 5 acting as a stopper. The value ofthe gap G at this point is approximately 5 μm. In order to inhibit thepenetration of moisture at the sealing section, it is preferable thatthe gap G be set at 5 μm±1 μm, and, more preferably, 5 μm±0.3 μm. At thesubsequent period, T₇, while the pressure is continued to be applied,the ultraviolet light source 23 is switched on at time t₆ to start theirradiating of ultraviolet light onto the affixing surface through aninfrared cut filter (not shown). The ultraviolet irradiation iscontinued for the duration of the period T₇, that is, until time t₇.

[0100] When the cross sectional shape of the adhesive 5 applied on thesubstrate is semicircular with a diameter of approximately 300 μm, thesize of the glass substrate 1 is 300 mm×400 mm, and it is desired toobtain 9-96 display substrates 3 by cutting after the sealing process,the pressures applied to the affixing surface during the pressureretaining periods T₂, T₄, and T₆ respectively are, as shown in FIG. 9,0.2 kgw/cm², 0.4 kgw/cm², and 0.5 kgw/cm². The durations for each of theperiods in the pressure application pattern are, from period T₁ toperiod T₆, 5 seconds, 5 seconds, 10 seconds, 5 seconds, 5 seconds, and 5seconds, respectively. In other words, the lengths of pressure retainingperiods T₂, T₄, and T₆ are set at a ratio of 1:1:1. In order to obtainuniform gap G and uniform seal line width W (refer to FIG. 2) at thesealing section by the adhesive 5 to secure the sealing quality, thepresent inventors have found that it is desirable to set the abovevalues within a range of ±20% for the pressure and a range of ±50% forthe duration. The present inventors have also found that, for theultraviolet irradiation period T₇, when the ultraviolet illumination isapproximately 100 mW/cm², it is desirable to set the length of period T₇to 60 seconds in order to obtain satisfactory curing of the adhesive 5.

[0101] Although in the above description, the pressure is represented inunits of force of kilogram weight per square centimeter, that is,[kgw/cm²] for ease of description, the values for pressure can beconverted into units of pascal, [Pa], which is the SI unit of pressureby multiplying by a constant 98066.5. For example, 0.2 kgw/cm² can beconverted into 19.6 kPa, 0.4 kgw/cm² can be converted into 39.2 kPa, and0.5 kgw/cm² can be converted into 49.0 kPa.

[0102] As described, in the second embodiment, because pressure isapplied between the glass substrate 1 and the sealing glass 4 in stagesand the adhesive 5 is then cured, a more uniform gap G and a moreuniform seal line width W can be obtained at the sealing section betweenthe glass substrate 1 and the sealing glass 4 by the adhesive 5.

[0103] For reference, the mechanism through which the uniform gap G anduniform seal line width W can be obtained at the sealing section willnow be described referring to FIG. 10. FIG. 10 schematically shows thecondition at the sealing section in which a pressure is applied to theadhesive 5 by the glass substrate 1 and the sealing glass 4. As shown inFIG. 10, for an adhesive 5 which has an approximately semicircular crosssectional shape immediately after application, initially, the area ofthe contact between the adhesive and the surface of the glass above theadhesive is small. Consequently, the adhesive 5 can be easily deformedeven when a pressure of small magnitude is applied to the glasssubstrate 1 (refer to period T₁ in FIG. 9). As the sealing section ispressed and the gap G is narrowed, however, the area of contact betweenthe adhesive and the surface of the glass above the adhesive becomeslarger, requiring a pressure of a larger magnitude (refer to periods T₃and T₅ in FIG. 9). On the other hand, the highly viscous, elasticadhesive 5 deforms slowly to respond with a certain delay in time to theapplied pressure. To this end, by retaining the increased pressure afterthe pressure to be applied is increased for a predetermined period oftime (refer to periods T₂ and T₄ in FIG. 9), it is possible to securetime for the adhesive 5 to deform in response to the pressure change.Because the pressure is increased to the next stage after the retainingperiod, the shape of the adhesive 5 can change smoothly, and,consequently, the gap G and the seal line width W become uniform.

[0104] Normally, gas is present inside the sealing space. As the gap Gis narrowed, the pressure increases and the gas attempts to escapeoutside. This attempt causes the sealing defect (A) as shown in FIG. 3.With the above method of the second embodiment, however, because it ispossible to prevent rapid pressure increase through the pressureretaining periods (periods T₂, T₄, and T₆ in FIG. 9), the generation ofsealing defects can be avoided. Therefore, generation of the sealingdefect (A) or the like can be desirably avoided.

[0105] In FIG. 10, a configuration is shown in which the cross sectionalshape of the adhesive 5 applied to the sealing glass 4 is approximatelysemi-circular immediately after the application, but, in general, theprinciple as described above is also applicable to other shapes such as,for example, a circular shape.

[0106] In addition, in order to simply secure the sealing quality, it isalso possible to omit the pressure retaining period and slowly andcontinuously increase the pressure to be applied to reach apredetermined pressure. Such a configuration, however, requires arelatively very long time for manufacturing a display panel.

[0107] Also, in the second embodiment, it is possible to form an organicEL element layer having a structure as described in the first embodimenton the display substrate to construct an organic EL display panel.

[0108] As described, according to the method for manufacturing a displaypanel in the second embodiment, the following advantages can be obtainedin addition to those that can be obtained through the first embodiment.

[0109] (6) When the glass substrate 1 and the sealing glass 4 areaffixed using an adhesive 5, in addition to the adjustment of theviscosity of the adhesive 5 by the temperature control, the applicationpattern of the pressure for pressurizing the affixing surfaces for theglass substrate 1 and the sealing glass 4 is set as a repeated patternof pressure changing periods and pressure retaining periods which followthe pressure changing periods. Because of this, it is possible topreferably secure the time for allowing the highly viscous adhesive 5 todeform in response to the applied pressure, which, in turn, allows foruniform gap G and uniform seal line width W at the sealing section in ashorter length of time.

[0110] (7) When applying a pressure to the affixing surfaces, it ispossible to secure, in the pressure retaining period, sufficient timefor the gas present in the sealing space to escape to the outside.Because of this, it is possible to prevent pressurized gas to remainwithin the sealed space.

[0111] (8) The sealing section having uniform gap G and uniform sealline width W obtained in this manner is even more reliable and, thus, itis possible to maintain, for a long period of time, predeterminedcharacteristics as a display panel.

[0112] (Other Embodiments)

[0113] The above embodiments can be suitably modified and applied asfollows.

[0114] In the above embodiments, nitrogen gas is used as the gas to fillinside the chamber 20. However, the present invention is not limited tosuch a configuration. As long as the gas is an inert gas that has lowmoisture content and does not adversely affect the display substrate 3,any gas, for example, a noble gas such as Ar, can be used in place ofthe nitrogen gas.

[0115] In the above embodiments, an example is shown in which a displaysubstrate 3 onto which an organic EL element is formed is sealed.However, the present invention is not limited to such a configuration.For example, the method according to the present invention can beapplied for sealing a display substrate onto which an inorganic ELelement is formed as a light emitting element, a liquid crystal displaysubstrate, or a plasma display substrate. The material of the substratewhich forms the formation surface for the display element is not limitedto glass as described in the above examples as a glass substrate 1, anda suitable transparent resin substrate which transmits, for example,ultraviolet or other appropriate light may be used.

[0116] In the above embodiments, a sealing glass 4 is used as thesealing member for sealing the display substrate 3. However, the presentinvention is not limited to such a configuration. For example, thedisplay substrate 3 may be sealed using a metal casing (metal can). Inthis case, an adhesive suitable for the sealing member can be selected.

[0117] In the above embodiments, an epoxy resin is used as theultraviolet curable adhesive for affixing the display substrate 3 andthe sealing glass 4. The present invention, however, is not limited tosuch a configuration, and, in addition to the epoxy resin, anyultraviolet curable resin which can be cured by irradiation ofultraviolet light and which does not adversely affect the displaysubstrate 3 can be used as the adhesive, including, but not limited to,a polyurethane resin, a polyester resin, and an acrylic resin.

[0118] In the above embodiments, an example structure of the elementlayer 2 to be formed on the display substrate 3 is described. However,the present invention is not limited to such a configuration, and theelement layer can be formed in any construction.

[0119] In the example of the first embodiment, the temperature in whichthe sealing process is performed is set at 35° C. However, the presentinvention is not limited to that temperature. It is preferable that thetemperature be set in a range in which the characteristics of theorganic EL element formed on the display substrate 3 are not degradedand the viscosity of the adhesive 5 is at an appropriate level, forexample, between 27° C. and 55° C. It is still more preferable that thetemperature is set between 29° C. and 40° C. Moreover, in order tostably obtain uniform gap G and uniform seal line width W at the sealingsection and to shorten the length of time to complete the sealingprocess, it is most preferable to set the temperature in the rangebetween 32° C. and 38° C. When an organic EL element 60 is to be formedusing the materials described in the first embodiment, it is preferablethat the sealing temperature be set at approximately 95° C. or less inorder to prevent degradation in the characteristics in each of thelayers, although the specific set temperature depends on the material ofthe EL element.

[0120] Moreover, in the first embodiment as described above, thetemperature during the sealing process is controlled to be at a constantvalue. However, the present invention is not limited to such aconfiguration. It is possible to actively vary the temperature so thatthe viscosity of the adhesive 5 used for the sealing process is suitablefor the sealing process and to obtain advantages similar to those in thefirst embodiment. In this configuration, it is desirable that thetemperature be controlled within the range in which the display elementsuch as the EL element is not adversely affected.

[0121] In the example of the second embodiment described above, thetemperature control for reducing the viscosity of the adhesive 5 isperformed by controlling the temperature of nitrogen gas filled into thechamber 20. However, the present invention is not limited to such aconfiguration. For example, as shown respectively in FIGS. 11 and 12, itis also possible to locally heat the adhesive 5 using one or moreheaters or an infrared light. In this manner, it is possible to minimizethe degradation in characteristics of the organic EL element caused bythe heating of the organic EL element. In the example configurationshown in FIG. 11, one or more heaters 27 are embedded within a quartzglass 11 a below the sealing glass 4, at positions corresponding to thepositions on the sealing glass 4 where the adhesive 5 is applied. Withthis configuration, it is also possible to employ other heat sourcessuch as, for example, a heat pipe, in place of the heater 27 embeddedwithin the quartz glass 11 a. In the example shown in FIG. 12, thestructure is configured so that infrared light irradiated from aninfrared light source 28 is irradiated onto only the adhesive 5 throughan infrared irradiation mask 29. According to these methods formanufacturing, because in both configurations, the adhesive 5 is locallyheated, it is possible to shorten the length of time for manufacturing adisplay panel while maintaining the quality as an organic EL displaydevice by minimizing rise in the temperature of the organic EL element.It is also possible that, in the device structure shown in FIG. 11 orFIG. 12, the pressure controller 25, instead of controlling the pressurechange over time as in the second embodiment, simply applies a constantpressure which is set in advance to the glass substrate 1 via thesupporting member 7. Also, the pressure controller 25 may be omitted asin the first embodiment.

[0122] In the examples illustrating the second embodiment as describedabove, the final pressure retaining period T₆ is set as a time perioduntil the gap G between the affixing surfaces of the glass substrate 1and the sealing glass 4 reaches a predetermined value (target value).However, the present invention is not limited to these configurations.For example, it is possible to further provide an additional sensor orthe like for monitoring the gap G and allow the curing process of theadhesive 5 to start based on a feedback value of the gap G from thesensor or the like. In this manner, it is possible to immediately startcuring the adhesive 5 after the gap G has reached the target value, tothereby further shorten the length of time required for sealing.Moreover, the curing process for the adhesive 5 need not be startedafter the gap G has reached the target value, and it is also possible toset the timing so that the gap G reaches the target value during thecuring process of the adhesive.

[0123] In the second embodiment as described above, an example pressureapplication pattern to the affixing surface between the glass substrate1 and the sealing glass 4 has been described. The application patternsin the embodiment is not, however, limited to the example applicationpattern. For example, it is also possible to set the pressure retainingperiods to be not equal and independently at different lengths, such asin a ratio of 1:2:3. Alternatively, it is also possible to set thepressure retaining periods such that a later period is longer in orderto create deformation periods sufficient for even an adhesive whoseviscosity is not as readily reduced by heating, and to thereby furtherimprove precision. In addition, although the pressure changing periodand the pressure retaining period are repeated for three cycles in thepressure application patterns in the above second embodiment, it is alsopossible to set the pressure application pattern to repeat differentnumber of cycles, for example, two or four or more. Also, the amount ofchange (amount of increase) of pressure for the final pressure changingperiod need not be less than the amount of change (amount of increase)of pressure during the preceding pressure changing periods. Also, therate of change of the pressure need not be constant. In other words, inat least one of the pressure changing periods, the rate of change of thepressure maybe actively set to be variable. Furthermore, the change inpressure for allowing the applied pressure to reach a target value neednot be monotonically increasing, and, in some cases, a period in whichthe pressure is reduced may be present. In summary, any setting can beemployed as long as uniform gap G and uniform seal line width W can bestably obtained between the glass substrate 1 and sealing glass 4 basedon the application, in stages, of pressure for pressurizing the affixingsurfaces between the glass substrate 1 and sealing glass 4.

[0124] In the description of the above second embodiment, a time periodfor allowing the adhesive 5 to follow the applied pressure to deform isprovided by providing pressure retaining periods. However, the presentinvention is not limited to such a configuration and it is possible, forexample, to set the process so that the movement of the glass substrate1 (and supporting member 7) is stopped while the adhesive 5 is beingdeformed.

What is claimed is:
 1. A method for manufacturing a display device inwhich an element substrate and a sealing substrate are affixed via anadhesive therebetween, wherein a display element is formed on saidelement substrate, said sealing substrate is placed to oppose saidelement substrate at the side onto which said display element is formed,and said adhesive is provided at positions to surround the formationregion of the element; said element substrate and said sealing substrateaffixed to each other are pressed; and said adhesive is cured; andwherein an ultraviolet curable resin is used as said adhesive; and thetemperature of said adhesive is controlled before said adhesive is curedby irradiation of ultraviolet light.
 2. A method for manufacturing adisplay device according to claim 1, wherein said adhesive is heated toa predetermined temperature before said element substrate and saidsealing substrate affixed to each other via said adhesive therebetweenare pressed.
 3. A method for manufacturing a display device according toclaim 1, wherein said adhesive is heated to a predetermined temperaturewhile said element substrate and said sealing substrate affixed to eachother via said adhesive therebetween are pressed.
 4. A method formanufacturing a display device according to claim 1, wherein saidadhesive is heated to a predetermined temperature in which thecharacteristics of the electroluminescence element formed as the displayelement are not degraded before said element substrate and said sealingsubstrate affixed to each other via said adhesive therebetween arepressed.
 5. A method for manufacturing a display device according toclaim 1, wherein said adhesive is heated to a predetermined temperaturein which the characteristics of the electroluminescence element formedas the display element are not degraded while said element substrate andsaid sealing substrate affixed to each other via said adhesivetherebetween are pressed.
 6. A method for manufacturing a display deviceaccording to claim 1, wherein the temperature of said adhesive iscontrolled based on application conditions of the pressure for pressingsaid element substrate and said sealing substrate.
 7. A method formanufacturing a display device according to claim 6, wherein thetemperature of said adhesive is set at a temperature in which thecharacteristics of the electroluminescence element formed as the displayelement are not degraded.
 8. A method for manufacturing a display deviceaccording to claim 1, wherein the pressure for pressing said elementsubstrate and said sealing substrate is changed over time until a targetgap is achieved between said element substrate and sealing substrateaffixed to each other.
 9. A method for manufacturing a display deviceaccording to claim 8, wherein said pressure for pressing said elementsubstrate and said sealing substrate is changed over time by repeating apressure changing period in which the pressure is changed and a pressureretaining period in which a constant pressure is maintained.
 10. Amethod for manufacturing a display device according to claim 9, whereina plurality of said pressure changing periods and a plurality of saidpressure retaining periods are repeated; and the duration of each ofsaid plurality of pressure retaining periods is independently set to anarbitrary length.
 11. A method for manufacturing a display deviceaccording to claim 9, wherein a plurality of said pressure changingperiods and a plurality of said pressure retaining periods are repeated;and the amount of change in pressure for each of said plurality ofpressure changing periods is independently set to an arbitrary value.12. A method for manufacturing a display device according to claim 11,wherein said amount of change in pressure for a final pressure changingperiod among said plurality of pressure changing periods is smaller thanthe amount of change in pressure for any previous pressure changingperiod.
 13. A method for manufacturing a display device according toclaim 8, wherein the rate of change of pressure in at least one of saidplurality of pressure changing periods differs from a rate of change ofpressure in the other periods.
 14. A method for manufacturing a displaydevice according to claim 9, wherein said pressure is changed over timethrough 3 repetitions of pressure changing periods in which pressure ischanged and pressure retaining periods in which a constant pressure ismaintained.
 15. A method for manufacturing a display device according toclaim 1, wherein said adhesive is a cation polymerizing, ultravioletcurable epoxy resin.